Modern automotive head units can connect with a portable computing device (e.g., a smartphone) through either a wired connection (e.g., a universal serial bus, USB, cable) or through a wireless connection (e.g., a Bluetooth connection) to play audio content from an application running on the portable computing device, which is converted to sound through the vehicle's speaker system. Such playback of audio content can be halted and then resumed, by the user manually selecting a pause or stop button and then a play button. The playback can also be halted automatically when the portable computing device is disconnected from the head unit. A process running in the portable computing device monitors the “last playing audio application”, by updating a data structure that identifies the application that is in foreground and currently playing audio. Examples include a music player application, a podcast application, and a music streaming application.
When the portable computing device connects to the head unit, the head unit may send a command to the portable computing device to start playing audio. In many cases, the portable computing device responds by playing audio from the application that is currently running in the foreground. Some head units will request a list of songs stored in a music library of the portable computing device and then send a command to the portable computing device to play the first song in the list (e.g., first song alphabetically). In both of these cases, the decision of which application to play audio from is determined simplistically, and more often than not, the decision does not meet the desires of the user. Other head units do not automatically request audio playback to begin, when the portable computing device connects to the head unit, but instead wait for the user to manually choose what application to play audio from, which may inconvenience the user.